Yoi. 54.] MR. F. A. BATHER ON PETALOCRINUS. 427 



18 mm. Greatest width, 19-6 mm. Width of facet, (?)2'75 mm. ; 



depth unknown. 



Number of finials visible : 12 on right side (left in text-fig. 10, 



which is reversed so as to make it comparable 



with the other diagrams), 13 on left side. -.-,. -.^ p f i 



Total visible, 25. There were probably 11 on ^^^: ^^' ~ \^^^^^- 

 .,, -J 1 • OQ • „n cnnus inferior, 



either side, making zo m all. 7? t - 7 i 



Ansrle of fan about 70° : it cannot be esti- ,, ^ ^ ,, ^^^^'^^9 

 1. J 1 ii, •;! • • of arm-fan. 



mated very easily, as the sides are missing. -^ •^ 



Angle of facet unknown. 



Ridges and grooves widen distalwards. At 

 the distal margin five mediad ridges with their 

 grooves have a united width of 4-2 mm., and 

 four external ridges and grooves have a united 

 width of 4-5 mm. 



The concavity of the specimen (^. e. convexity [Nat. size.] 



of the ventral surface) is marked and equable. 



Eolations to other Species. — The number of finials separates 

 this from P. mirahilis with 16, and P. vishycensis, with at most 22. 

 Prom P. vishycensis senior, which has about the same number of 

 finials, it differs in its regularit}" of branching and absence of senile 

 characters. The length and width of the fan have about the same 

 proportion as in P. vishycensis, but in P. inferior the width of the 

 facet was probably greater, and the width of the grooves and ridges 

 slightly less (in consequence of their greater number). 



P. mirabilis, Weller. 

 (PI. XXYI, figs. 37-56.) 



Angle of arm-fan 51° to 83°, usually 71° to 78° ; fan bilaterally 

 symmetrical in shape and arrangement of grooves ; finials 16 ; 

 ventral surface of fan convex, more so than in P. vishycensis ; dorsal 

 surface slightly concave or flattened, no growth-lines or ornament 

 seen ; ridges usually less wide than grooves, and with rounded tops. 



Xo specimen was selected as holotype by the author of the 

 species. 



Co-types are specimens a, b, collection of Mrs. A. D. Davidson, 

 deposited on loan in the Walker Museum, University of Chicago, 

 and specimens g and h in that Museum. 



M eta-types are specimens d, e, f, i in the Walker Museum ; 

 j, k, 1 in the British Museum ; and c in the Davidson Collection. 

 Eor details, see pp. 405, 406. 



Locality: Near Monticello, Jones Co., la. (U.S.A.). 



Horizon : Niagara Limestone, upper beds. 



Measurements: For those of the arm-faas, see the following 

 table : — 



